MELBOURNE, Australia — Maria Sharapova leaned back and pumped her arms. She ripped her elbows back and forth, screaming after her victory. Four pumps, five — she rocked forward — six pumps. More.

Sharapova had just defeated Venus Williams 6-1, 6-3 Friday, her first victory over the seven-time major winner in a Grand Slam. This was a match clearly worth celebrating, but it was if Sharapova had won the Australian Open title eight days early.

“I was just really pumped,” she said. “Why shouldn’t I be?”

After back-to-back 6-0, 6-0 wins in the first two rounds — the first time that happened at major since 1985 — Sharapova has conceded the fewest number of games en route to the fourth round at the Australian Open since Steffi Graf did so 24 years ago. Graf also lost only four games in her first three matches on her way to the second of her three consecutive titles in Melbourne.

Sharapova knows she must stay on top of her game. Another Williams could be waiting. Since Sharapova won the French Open, to complete a career Grand Slam of all four major titles, Serena Williams has won just about everything.

Asked if she was thinking about a showdown with the younger of the Williams sisters, Sharapova said: “She’s on the other side of the draw, and other players are on the other side of the draw as well.”

That means they can meet only in the final.

“Until you get to that stage, and if you do, if you’re facing each other,” she said, “that’s the point when you’re thinking about that particular opponent.”

The top two contenders on the opposite side of the draw, defending champion Victoria Azarenka and Serena Williams, play one after the other at Rod Laver Arena on Saturday. Top-ranked Azarenka is first up against American Jamie Hampton, followed by Williams against Ayumi Morita of Japan.

U.S. Open champion Andy Murray follows them in a third-round match against occasional hitting partner Ricardas Berankis, a qualifier from Lithuania. Four-time Australian Open champion Roger Federer has the night match against Bernard Tomic, the last Aussie in the men’s or women’s draws.

Top-ranked Novak Djokovic took another step closer to a third consecutive Australian title, defeating Radek Stepanek 6-4, 6-3, 7-5 in the third round.

His victory came on the same day Lance Armstrong admitted during a television interview with Oprah Winfrey that he used banned drugs to win his seven Tour de France titles. Djokovic, a lifetime cycling fan, said at his post-match news conference that it was “a disgrace for the sport to have an athlete like this.”

“He cheated the sport,” Djokovic said. “He cheated many people around the world with his career, with his life story.”

Djokovic did not have an easy time against the 31st-seeded Stepanek and was troubled at times by the Czech’s serve-and-volley game. But Djokovic came out laughing, and he embraced his opponent over the net at the end. Stepanek even had chair umpire Carlos Bernardes grinning after producing an unexpected, over-the-shoulder winner to save one match point in the last game.

“Absolutely, it was great. Great match and great fun,” Djokovic said. “It’s always tricky to play Radek. He’s a talented player. Skillful player.”

Stepanek won 36 of the 67 points he played at the net, forcing Djokovic out of his comfort zone at the back of the court and making him work for every point.

“He’s skillful on the net and he was not giving me a lot of rhythm — he was changing up the pace on the ball,” Djokovic said. “Nowadays everything is based on the baseline. It’s nice to see somebody coming to the net.”

Djokovic will play Sunday against No. 15 Stanislas Wawrinka, who knocked out the last American man in the draw with a 7-6 (6), 7-5, 6-4 win over No. 20 Sam Querrey. For the second straight year, there will be no American men in the fourth round at Melbourne Park.

In the last match of the day, fourth-seeded David Ferrer finished off a 6-4, 6-2, 6-3 win over 2006 Australian finalist Marcos Baghdatis with an ace, advancing to a fourth-round match against Japan’s Kei Nishikori.

In an all-Serbian match of two former No. 1 women, 2008 French Open champion Ana Ivanovic beat Jelena Jankovic 7-5, 6-3. She moved into the fourth round against Poland’s Angieszka Radwanska, who is seeded No. 4 and won her 12th straight match — including titles at Auckland and Sydney — with a 6-3, 6-1 defeat of Britain’s Heather Watson.

No. 5 Angelique Kerber and No. 19 Ekaterina Makarova, two of the four women who beat Serena Williams in 2012, will meet in the fourth round. Kerber stopped 17-year-old American Madison Keys 6-2, 7-5 in the opening match at Rod Laver Arena, then blew out the candles on a cake to celebrate her 25th birthday. The crowd sang “Happy Birthday.”

Makarova, who beat Williams in the fourth round in Australia last year, had a 6-7 (4), 6-3, 6-4 win over 2007 Wimbledon finalist Marion Bartoli.

All along, Sharapova had been preparing for this third-round match. She withdrew from an exhibition tournament and the Brisbane International with a sore collarbone, but hasn’t showed any signs of being troubled by it Melbourne.

“I think when we both looked at the draw, it was a matchup we were both looking forward to,” Sharapova said. “I was just really determined out there because I knew the tennis that she’s capable of producing and playing. She’s a tremendous athlete and a great champion.”

Sharapova’s exuberant celebrations had little effect on Venus Williams. She barely acknowledged it as she made her way from the court.

“Definitely not my best today, but there’s always other days to play better,” she said. “I just had a lot of errors. ... That never helps.”